A great act is tough to follow and sometimes delivering two great devices in a row requires that you take a completely different approach with the successor. Now on its third "flagship killer" (with the OnePlus X taking a different path), OnePlus has taken on the tough task to mature from a business standpoint, while still retaining that ambitious "never settle" attitude that brought it where it is today.
Source: http://www.gsmarena.com/oneplus_3-review-1455.php